Different Languages for Each Student

I was thinking of incorporating DuoLingo in an elementary classroom by letting students choose a language they want to use during free time. Is it possible to have students in one class learning different languages or do I need to have separate classes for each language? If I wanted ELLs to work on English would they also need a separate class?

I'm starting a new school year in a week, but it is unifying in my opinion. Some are motivated by the points. They can adjust settings to be friends/observers of the progress of others--same as a regular user. The unity I was able to encourage was among those studying the same language. Anyway, I'm at school, so I must get back to work. Peace! (Personally, I have just kept my Spanish tree progress at a minimum during the summer with a streak of 110 days--on my main account, without the "1".)